Regional Anaesthesia

Types of regional anaesthesia

Regional anaesthesia can be subdivided into:

• Neuraxial regional anaesthesia
• Nerve plexus blocks
• Peripheral nerve blocks

Regional anaesthesia can be distinguished from local anaesthesia which involves injection of local anaesthetic infiltrated in to the skin and subcutaneous tissues which are to be numbed.

Neuraxial regional anaesthesia

Neuraxial regional anaesthesia can be subdivided into spinal anaesthetic techniques and epidural anaesthesia. In these techniques local anaesthetic is injected either into the subarachnoid space or the epidural space.

A relatively small volume of local anaesthetic is required for spinal anaesthesia because the subarachnoid space is filled with cerebrospinal fluid, which distributes the local anaesthetic around the spinal column and spinal nerves as they leave the spinal column.

The epidural space surrounds the subarachnoid space and the spinal nerves pass through the epidural space from the spinal cord to form the peripheral nerves supplying the trunk and limbs.

Spinal anaesthesia is used for surgical procedures on the lower part of the abdomen, pelvis and lower limbs. In theory, an epidural anaesthetic can be placed to block the cervical, thoracic, lumbar or sacral nerves or combinations of these. Cervical epidural anaesthesia, however, is rarely used because of the risks of the technique.

Nerve plexus blocks

The most common site for plexus blocks is the brachial plexus. The brachial plexus is formed by spinal nerves from the neck and upper thoracic level and they eventually supply the peripheral nerves of the upper limb. The brachial plexus can be blocked through approaches in the neck, above the clavicle, below the clavicle or in the axilla. Brachial plexus block is now very commonly used for surgical procedures on the upper limb.

When I began my training in anaesthesia, plexus blocks and major peripheral nerve blocks were infrequently performed. This was because techniques were “blind” and success rates variable. Correct placement of the local anaesthetic depended on the anaesthetist’s knowledge of anatomy, their experience and a bit of luck.

Peripheral nerve blocks

In the late 1980s, peripheral nerve stimulation was used by applying a small electric current through the nerve block needle. When the nerve block needle contacted the nerve, it stimulated the nerve causing contraction of the muscle supplied by that nerve.

In the early 2000s I was among the first anaesthetists in the UK to introduce ultrasound guided nerve block techniques. This became possible because of the availability of portable ultrasound machines, which were initially introduced into operating theatres to aid insertion of vascular lines.

When I realised the potential for ultrasound guided regional anaesthesia I approached radiology colleagues with expertise in musculoskeletal imaging. At that time, their assumption was that nerves were not identifiable using ultrasound but when we looked for them, much to my radiology colleague’s surprise, they were able to discern the nerve structures. Ultrasound guided techniques are now recognised as the gold standard for regional anaesthesia and have rapidly popularised brachial plexus blocks and other nerve blocks.

With Pawan Gupta and other colleagues I have been using the capability of ultrasound guided regional anaesthesia to systematically define the optimum dose of local anaesthetics for the blocks. These studies have used trial designs previously rarely used in anaesthesia. They have the potential to establish clinically useful dose levels while minimising the number of patients required for each study. The benefit of such studies is that we can increase the likelihood of achieving successful regional anaesthesia while minimising the risk of toxic effects of local anaesthetic drugs.

Case study: Using regional anaesthesia to help patients with rheumatoid arthritis

I started using regional anaesthetic techniques on a routine basis well before the availability of portable ultrasound machines. This was because I started working with a hand surgical colleague, Simon Knight, whose practice included many patients with rheumatoid arthritis requiring hand surgery for disabling abnormalities.

Rheumatoid arthritis is a disease that affects principally the joints but which can have effects on other body systems, including the heart and lungs, which increase the risk of anaesthesia. Rheumatoid disease affecting the joints of the neck, jaw and voicebox also place specific risks to these patients when they require anaesthesia. The ability to provide regional anaesthesia obviated many of these risks.

The advent of ultrasound guidance has enabled many more anaesthetists to be proficient in regional anaesthesia. The consequence of this is that more patients requiring a variety of operations are potentially provided with a choice between a regional and general anaesthetic. In discussing anaesthetic options with the patient the anaesthetist needs to present to them the benefits of each technique and its potential complications.

Benefits of regional anaesthesia

Evidence has shown many short-term benefits of regional anaesthetic techniques in terms of pain relief and early mobilisation following orthopaedic procedures.

However, there is uncertainty whether regional anaesthesia has benefits in terms of functional outcomes from orthopaedic procedures. In situations where plexus blocks or peripheral nerve blocks can avoid a general anaesthetic, then the risks of general anaesthesia are avoided.

The situation with neuraxial regional anaesthesia is less clear. The NAP4 audit of regional anaesthesia conducted by the Royal College of Anaesthetists demonstrated the finite serious risks of neuraxial regional anaesthesia: these are permanent paralysis or death.

In an editorial for the British Journal of anaesthesia, I argued that when contrasting general anaesthesia with neuraxial anaesthesia, the balance of risks is patient specific. In general terms the healthier and fitter the patient the balance is more shifted towards general anaesthesia, whereas with increasing patient comorbidity the risks tend to favour neuraxial anaestheisa.

The situation becomes even more complex when determining the benefits of combining neuraxial anaesthesia with general anaesthesia, for example, in major abdominal surgery. The likely benefits here are even more dependent on patient specific factors and indeed the specific nature of the surgical procedure.